The ultimate goal of this work is to increase the success rate of the microelectrode-guided surgery and consequently improve the quality of life of patients suffering from movement disorders. To achieve this goal, methods are proposed to augment the navigational accuracy of the surgery without interfering with standard portions of the procedure. To successfully target a specific brain location (e.g. the best location for implantation of a permanent stimulating electrode), one needs to accurately know the boundaries of the neighboring structures of interest (in this case: Basal Ganglia, Thalamus, Sub-thalamus, optic tract). In the standard procedure, these boundaries are obtained from a brain atlas. However, the accuracy of the 3rocedure is adversely affected by: the shape and size difference in anatomy of the brain atlas and of the 3atient, and by intraoperative brain deformation. To address these problems the following aims are proposed: AIM 1. Available brain atlases will be explored and the highest-resolution one will be selected. A method for building 3D surface models of the structures of interest from the atlas images will be designed. The atlas will be represented by its images stacked into a 3D image volume and by a collection of 3D surface models. AIM 2. A highly accurate method for nonrigid alignment of the atlas 3D image and the patient's preoperative MR scan will be developed. This alignment will be applied to the atlas models to adjust their position, shape, and size. This will bring the models into registration with the patient MR scan making them patient specific. AIM 3. The locations of boundaries between structures of interest along the microelectrode tracks are recorded intraoperatively. This information will be used to fine-tune the patient specific models in order to make them more accurate. AIM 4. The intraoperative brain deformation will be analyzed, its affect on the accuracy of the microelectrode-guided surgery will be investigated, and methods for its compensation will be explored. AIM 5. The proposed methods will be clinically tested on 50 cases of microelectrode-guided surgery. Although the proposed methods will be applied to the microelectrode-guided surgery, they can be extended to other image-guided neurosurgical procedures, including tumor removal and epilepsy surgery.